Magnetic separator



May 15, 1934. c PAYNE 1,958,521

MAGNETIC SEPARATOR Filed Oct. 31, 1931 2 Sheets-Sheet l l/Vl/Z-WTOR 67areme Q v y 1934- c. Q. PAYNE 1,958,521'

MAGNETIC SEPARATOR 7 Filed 001.. 31, 1931 2 Sheets-Sheet 2 Patented May15, 1934 UNITED", STATES PATENT OFFICE 9 Claims.

This invention relates to improvements in magnetic separators, andparticularly to the separation of minerals of low magneticsusceptibility which require a highly intense magnetic field in order toact upon them.

It is the object of the invention to provide a magnetic separator inwhich the particles to be separated, in passing over the rotor andbetween the pole pieces, are subjected to a continuous intense magneticinfluence, but one which involves only a minimum movement of theattracted particles relative to the rotor surface.

Another object of the invention is to provide a magnetic separator ofthe type herein described,

in which point and edge convergences of magnetic flux-density are set upat spaced intervals both axially and circumferentially of the rotorwhereby particles of low magnetic susceptibility are attracted andseparated from non-magnetic particles more completely than in machinesheretofore used in this field.

Another object of the invention is to provide a magnetic separator ofthe type described, in which wear upon the rotor due to abrasion by theparticles undergoing separation will not materially alter the magneticinfluence to which the particles are subjected.

Various other objects and advantages of the invention will appear asthis description proceeds.

Referring now to the accompanying drawings which show a preferred formof embodiment of the invention from which however various modificationsand changes may be made, without departing from the scope thereof:

Figure 1 is a cross-section on line 1--1 of Figure 2,

Figure 2 is a cross-section substantially on the line 2-2 of Figure 1,showing an embodiment of the invention which employs'two bipolarelectromagnets, and two rotor-armatures placed between opposingpolepieces,

Figure 3 is an enlarged cross-section of a rotor and its polepieces withdiagrammatic view of the magnetic flux-circuit passing through them,

Figure 4 shows a segment of the interleaved discs of the rotor providedwith blunt toothed edges. and

Figures 5 and 6 illustrate diagrammatically the concentration of thefiux density at the points and edges of the interleaved discs.

The separator consists essentially in improved means for attractingmagnetizable particles in controlling their movements while they arewith- 55 in the magnetic field and in removing them from the field. Italso consists in means for adjusting the width of the field-gap inrelation to the size of the mineral particles to be separated therein.It also consists in an effective combination of electromagnetic unitswhereby two magnetic fields are obtained on one magnetic flux circuit.

Magnetic separation is based on the movement of magnetizable particlesin or near a magnetic field, and is caused by differences of magneticdensity. Mineral particles differ widely in their relativeattractability, e. g. magnetite having several hundred times that ofgarnet. In the case of the feebly magnetic minerals with which thepresent invention is chiefly concerned, I have found that a highlyintense or highly convergent magnetic field such as that employed in thewell known Wetherill type of separator is not well adapted to secure aclean separating action. The magnetic flux of such a field acts as awhole, and in the presentation of the ore mixture the attractedparticles must be lifted against gravity a considerable distancerelative to their size during a very short interval of time. I havefound it far more effective to localize or subdivide the attractingpower of the field by means of a large number of inductively magnetizeddiscs which expose magnetized edges and points and which are interleavedwith non-magnetic discs, of such thickness that a, magnetizable particlerequires only a slight lateral movement to reach either of its boundingedges when placed between them. Such particles, moving with the rotationof the discs are more easily attracted and held while they are fallingunder the influence of gravity than when they are lifted against it.They can also thus be acted on during a more efiective interval of time.

In attaining the above purpose I employ a series of thin magnetic discs10 and non-magnetic discs 11, which are mounted on a shaft 12 and form arotor-armature 13, preferably between two opposing electromagnets 14 and15. These laminated discs also tend to suppress Foucault, or eddycurrents which would be generated if the armature were made of solidmetal and revolved at high speed. These currents cause resistance torotation and heating. The discs also form the separating drum on whichthe ore mixture is fed from the hopper 16 by means of the rotary feeder1'7. The chutes 18 and 19 serve to separate and space the feed streambefore it reaches the rotors 13--13. I also provide the edges of thesediscs 10 with a series of blunt longitudinal teeth 20 whose pitch is sogreat compared with their depth that the bounding edges both of thevalleys and also of the tops of these teeth areable to attract and holdmagnetic particles while passing through the magnetic field. The topsand valleys of these teeth form arcs or tangents of concentric circleswhose diameters differ only slightly from each other. These teeth alsoperform another important function in the separating action. Theirpoints, or corners S (Figure 5) afford a still greater attracting forcethan the edges since the magnetic flux is here super-saturated by reasonof its convergence from three directions. Any circumferential movementof the particles held to the tops or valleys of the discs" edges isstrongly resisted when they reach these point convergences of the fluxdensity.

Thus by reason of the spaced magnetic and nonmagnetic discs 10 and 11 anedge concentration of flux density is provided axially of the rotors ateach side edge of both the teeth and valleys of the discs 10, as isindicated graphically at e in Figures 5 and 6, and by providing thetooth projections 20 a greater convergence of the flux density issecured at the points of the teeth S than at their edges whereby anintense magnetic attraction at spaced intervals both longitudinally andcircumerentially of the rotor is brought about.

This greatly assists the removal of the attracted particles from thefield without interference with the non-attracted particles when theyhave reached the end of the field. In the case of strongly magneticparticles, it is quite a difiicult matter to remove them from a highlyintense magnetic field, especially, if they are attached to a smoothsupport. They then respond to the action of the magnetic field as awhole and a reverse movement is set up. This causes them to form columnsby inductive action under the contending forces, and as the tops of thecolumns get knocked off by the rush of the non-magnetic part of the feedstream at the exit of the field, the separating action is interferedwith. In the case of feebly magnetic particles a similar tendency"exists to a lesser degree.

the ore mixture while it is passing through the field. A wiper 32preferably of a rubber blade variety removes any strongly magneticparticles from the rotors 1313' which may have become mixed with thefeebly magnetic particles.

In my previous Patent No. 641,148, granted January 9, 1900, I have shownand claimed means for separating an ore mixture by means of pulsationsor undulations of magnetic density. These means comprised wedge shaped,or pyramidal teeth upon the separating carrier. I found in practicehowever, that serious objections developed to this construction. Theratio of the pitch to the depth of these teeth being only about one toone, or one and one-half to one, the valleys between the teeth were notavailable for separation. This facilitates the escape of magneticparticles between the pulsations, i. e. between the tooth edges.Moreover, the edges and points of the teeth being exposed to theattrition of the feed stream would gradually wear and become rounded,thus losing a certain amount of their effective holding power. In mypresent invention a practically continuous separating action is obtainedwith only a minimum relative movement of the magnetic particles whilethey are being attached and held to the highly charged disc edges. Forthis purpose the teeth 20, (Figure 4) are made quite blunt and shallow,the

ratio of their pitch P to depth 0 being quitelarge, viz: about ten toone. In this way both the boundingedges e. of the valleys and of thetops of the teeth form arcs or tangents of concentric circles whosediameters difier only slightly and they are both made available forseparation. Moreover, any wear of the tops of the blunt teeth byattrition from the feed stream does not reduce the sharpness of thepoints or of the bounding edges of the teeth, and they are thuscontinuously available for the purpose explained above.

It will be seen from Figure 3 that since the lines of force do notemerge from the disc edge at the neutral line lc-lc, of the rotorarmature 13, and since they reverse their polarity on opposite sides ofthe neutral line, no feebly magnetic particles can be held to the discedges beyondthis point.

My invention may be employed with various types or designs ofelectromagnets but I have preferred to illustrate it as shown in Figures1 and 2 by means of two bipolar electromaguets which are opposed, andhave their field coils so connected that when energized they form twomagnetic fields on the same magnetic flux circuit as shown by the brokenline and arrows in Figure 1. In this way, no interference is caused bythe magnet units with the two feed streams as they pass through theseparator fields, and the maximum capacity as well as the greateststructural economy is thus obtained.

The yokes A, B, of the electromagnets, Figures 1 and 2 may be supportedin any convenient way as upon the angle irons C C attached to the frameD D D D of the machine. The yokes are enabled in this way to slidereadily upon their supports in adjusting the widths of the field gaps.Each of the yokes A, B, has bolted to it the magnet cores A A B B andpolepieces A A B B The field-coils A A B B which surround the coresenable the two electromagnets to be energized. The rotor armatures 13and 13' revolve in the field gaps thus formed between the opposingpolepieces A B and A B. These rotor armatures also form the drums onwhich the material to be separated is fed by means of suitable guideplates 18 and 19 as shown in Figure 2. The rotors and polepieces are soproportioned and assembled that by extending the magnetic field asuflicient arc below the horizontal diameter of the rotors, theattracted particles are enabled to be discharged at a considerable angleof divergence from a vertical line as the feed stream leaves the field.Aided by centrifugal fo rce a clean separating action is thus obtained.The division plate 21 is located at a suitable distance below the rotorsfor this purpose and deflects the non-magnetic particles into throughthem. They are bolted to the ends of the polepieces A B and A B andsupport the full thrust of the bi-polar fields when the latter areenergized. Each bracket bearing 24 and 25 is provided with plates 26carrying a threaded bolt 27 and by means of shims 28 at the rear of eachone of the polepieces and by means of the thrust bolts 27, and lockingbolts 29 shown in Figure 2, the polepiece faces A and B may be moved sothat the width of the air gap on each side of the rotors can thus bevaried to suit the grain size of the material undergoing separation.Nonmagnetic guide brackets 30 and 31 through which the rotor shaftpasses without bearings for the shaft also support the inner ends of thepolepieces as shown in Figure l, and assist to maintain the opposingelectromagnets in horizontal alignment.

Figure 3 shows an enlarged section through one of the rotors and itsopposing polepieces, with diagrammatic views of the magnetic fluxthrough the rotor and polepieces in order to illustrate more clearly thecontrol of the fiux density which is obtained in the field gaps by meansof the thin interleaved magnetic and non-magnetic discs, and the teethon their edges. Figure 4 shows a few of the disc edges in perspectiveview on a still larger scale. I have found that by making the teeth ofthe disc edges quite shallow so that the ratio of their pitch P to theirdepth 0 is about ten to one, I obtain a strong attracting force byconvergence of the magnetic flux along the bounding edges of the discsboth at the valleys 10 as well as along the tops 20 of the teeth. Inthis way the separating action is practically a continuous one, and thedistance through which the magnetic particles require to be moved whilethey are in the field and before they are attached and held to the discsis extremely small. This greatly improves the separating action.Moreover, as already pointed out the comers or points of the teethcause'a still greater intensity of magnetic attraction upon the feeblymagnetic particles and any tendency'to slide backwards as they are movedout of the field, is thus resisted and overcome.

The operation of the separator will be quite clear from Figures 1, 2 and3. Here when the field coils A A B B have been energized by means of anelectric current, preferably from a dynamo-electric machine, the rotorarmatures 13 and 13' are caused to revolve in their fields in thedirection shown by the arrows by any convenient means such as a pulley12a and belt driven from an outside source of power. The material to beseparated is fed from a hopper 16, placed over each of therotor-armatures, and the products of the separation are collected inbins or discharged by chutes 22-23 below the machine. A regulatedfeed-stream of the granular material is conveyed by means of the guideplates 18 and 19 upon the rotor armatures 13, 13'. The width of thefield gap through which the feed-stream passes is regulated by means ofthe adjusting bolts and shims of the bearing brackets 24-25, whichsupport the full thrust of the bi-polar magnetic fields. In this waysuflicient clearance for free movement of the particles is providedallowing them to move beyond the influence of the edges of theinterleaved magnetic and non-magnetic discs of which the former arehighly magnetized by induction. The speed of the rotor is so regulatedthat the 'magnetic particles are aiIorded several opportunities of beingbrought into contact with the disc edges before they reach the dischargeend of the field which is located below the horizontal diameter of therotor so that the magnetic particles may be carried away from thenon-magnetic particles at a divergent angle-and over the division plate21 asshown in Figure 2, thus effecting a separation. In accomplishingthis result the thickness of the rotor discs, the blunt teeth of largepitch-depth ratio on their edges, and the regulation of the width of thefield-gap to suit the grain size of the feed-stream are the importantfeatures of my invention which secure a more perfect result in theseparation of the feebly magnetic minerals.

While I have shown a preferred form of embodiment .of my invention, I amaware that modiflcations may be made thereto and I therefore desireprotection on the scope and spirit thereof as described herein andclaimed hereinafter.

I claim:

1. A magnetic separator comprising two opposing bipolar electromagnets,two rotor armatures composed of interleaved magnetic and non-magneticdiscs and opposing polepieces between which said rotor armatures revolveand form parts of a single magnetic circuit generated by saidelectromagnets; in combination with means for varying the width of thefield gaps between said rotor armatures and said polepieces and meansfor controlling the flux density of the magnetic fields, along the discedges of said rotors by adjusted variations thereof, comprising bluntlongitudinal teeth upon said rotor surfaces,

whose ratio of pitch to depth enables the bounding edges both of thevalleys and of the tops of said magnetic disc teeth to attract and holdmagnetic particles fed upon said rotors while passing through saidfields, such ratio being at least ten to one.

2. In a magnetic separator of the type described including an opposedpole electromagnet and a rotor-armature mounted between the polefaces ofsaid electromagnet, a series of interleaved alternating magnetic andnonmagnetic disks constituting said armature, the edges of said diskshaving a continuous series of shallow blunt toothed projections, incombination with means for energizing said electromagnet and producingin the field gaps along the bounding edges of the tops, slopes andvalleys of the magnetic disks of said armature convergences of fluxdensity of substantially the same intensity while the corners of saidteeth, forming point intersections, produce convergences of greatermagnetic density.

3. A magnetic separator comprising an electromagnet, a rotor-armaturecomposed of interleaved magnetic and nonmagnetic disks, and opposingpole pieces between which said rotorarmature revolves, in combinationwith means for varying the width of the field gap between saidrotor-armature and said pole pieces, and means for concentrating theflux density of the magnetic field along the circumferential disk edgesof said rotor comprising blunt longitudinal teeth upon said rotorsurface whose ratio of pitch to depth permits the magnetic disk teeth tocontinuously attract and hold magnetic particles fed upon said rotor onboth the ridges and said rotor armature and said disks forming parts ofa single magnetic circuit generated by said electromagnet; incombination with means for concentrating the flux density of themagnetic field along the disk edges of said rotor comprising bluntlongitudinal teeth upon said rotor surface whose ratio of pitch to depthenables the bounding edges both of the valleys and of the tops of saidmagnetic disk teeth to attract and hold magnetic particles fed upon saidrotors while passing through said fields, such ratio being at least tento one.

5. A magnetic separator comprising an opposed pole electromagnet, aframe, supporting the magnetic poles, a. rotor armature mounted forrotation between said pole faces said poles being movably mounted onsaid frame, in combination with adjustable bearings for said armatureshaft, comprising non-magnetic compression brackets adjustably spacingsaid pole pieces and supporting said armature in balanced relationtherebetween, independent of'said frame against the tractive force ofsaid electromagnet and'means connected with said brackets to adjust thefield gaps between the armature and said pole faces, together with meansfor feeding material to be separated between the armature and a poleface.

6. A magnetic separator of. the class described having a bi-polar magnetand two magnetic fields adjacent the pole faces of said magnets, a framesupporting said magnet, and permitting movement of the magnet on theframe, said. magnetic fields being in a single magnetic circuit, anarmature rotatable between each pair of said pole facesand composed ofmagnetic and non-magnetic disks, means to produce line and pointconvergences of the magnetic flux density in each field, and means tosupport the armatures in balanced relation between said pole faces andindependentrof said frame comprising non-magnetic compression bracketssupporting the full thrust of said electromagnet and providing bearingsfor the armature shaft, said pole faces being relatively movable withrespect to said armature to adjust the field gaps.

, placed between said pole faces composed of a series of alternatingmagnetic and non-magnetic disks, each of said disks being provided witha series of shallow teeth whose tops form parts of the cylindricalsurface of saidarmature and whose outer corners form points of fluxconvergence of relatively great density, the valleys of the teeth of themagnetic disks also forming lines of fiux convergence of lesserdensity,'and means to support said armatures in balanced relationbetween said pole faces comprising non-magnetic compression bracketssupporting the full thrust of said fields and providing bearings for theshaft of said armature, and means connected with said brackets to adjustthe field gaps between said armatures and pole faces.

. 8. An armature for a magnetic separator of the class described andadapted for mounting between the pole faces of an electrorhagnet, saidarmature comprising a plurality of substantially cylindrical disks of amagnetic material and a plurality of similar shaped disks of anon-magnetic material, said magnetic disks and nonmagnetic disks beinginterleaved, each of said magnetic disks having shallow teeth andvalleys, the comers of the teeth forming a plurality of longitudinallines of relatively great flux convergence, and the tops and valleys ofthe teeth forming a plurality of circumferential lines of fluxconvergence of lesser density, said lines of lesser flux density beingsubstantially continuous in reaction on magnetic particles passingbetween the armature and a pole face, said transverse lines ofgreaterflux density being non-continuous in effect on magnetic particlespassing between the armature and a pole face.

9. A magnetic separator comprising a pair of oppositely positionedbi-polar electro-magnets with the N pole of each opposite the S pole of119 the other to form pairs of opposing pole faces between which twomagnetic fields are formed upon the same magnetic circuit, rotorarmatures placed between opposing @pole faces but each spaced from onepole face to provide a relatively large field gap, and a frame tosupport said electro-magnets separably and movably thereon in adjustablyspaced relation and said armatures in balanced relation between saidpole faces comprising non-magnetic compression brackets sup- 129 portingthe full thrust of said fields and providing bearings for saidarmatures, andmeans connected with said brackets to adjust the fieldgaps between said armatures and pole faces together with means forfeeding material to be separated to said relatively large field gaps.

' CLARENCE Q. PAYNE.

